Elecraft KXB3080 - Manual (Page 6)

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Rotate potentiometer R1 fully clockwise and check the resistance between ground and the part of the
cut trace that goes to the open solder pad for C27 and the center terminal of potentiometer R1. The
resistance must be greater than 800 ohms. If the resistance is low, check for a solder bridge between the pad
for capacitor CC and solder pad A or the adjacent pad for L6.
Cut a 20” (51 cm) length of the #28 red toroid wire. (The #28 is the smaller red wire.)
“Sew” the long end of the wire through the hole in one of the T37-2 toroid cores (red) for a total of 33
turns exactly as shown in Figure 4. Be sure you wind the turns the direction shown in the figure. Count one
turn for each time the wire passes through the center of the core. There are no half or quarter turns when
winding a toroid. The turns should fill about 90% of the toroid core as shown in the figure.
Cut a 3” (7.6 cm) length of the #26 green toroid wire. Strip the insulation from 1/2” (13mm) at one
end of the green wire (you’ll strip the insulation from the other end later). Use one of the following
methods to remove the insulation and tin the lead:
1. Heat Stripping:
a. Place a small amount of solder (a.k.a. a “blob” of solder) on your soldering iron.
b. Insert the clipped end of the wire into the hot solder so it touches the bare end of the wire. If
the iron is hot enough, you should see the insulation bubble and vaporize after 4 to 6 seconds.
c. Add solder and feed more wire into the solder as the enamel melts. After reaching the point
where you want the tinning to stop, slowly pull the wire out of the solder.
d. If any burnt enamel remains on the lead, scrape it away using your thumbnail or sharp tool.
2. Burning: The insulation can be burned off by heating it with a butane lighter for a few seconds.
Use sandpaper to remove the residue, then tin the bare wires.
3. Scraping: Use a sharp tool to scrape the insulation away. Work carefully and gently: do not nick
the wire. Remove all the enamel around the circumference of the wire, then tin the bare wire.
The stripped end of the green wire is end 2 as shown in Figure 4. Position the green wire so the
stripped end extends right up to the point where the wire passes into the center of the core, then wrap the
long end of the wire around the toroid and through the center one more time to make two turns.